The cross section for photoionization of the π g2 p electron of O 2 is calculated from threshold to about 60 Å wavelength of the incident radiation, thus complementing some previous results. The transition strengths of various continua for initial π g2 p, π u2 p, σ g2 p and σ u2 s M.O.'s are also given and used to interpret Rydberg series of O 2( X 3Σ - g). A preliminary result for the threshold cross section of NO( X 2Π r) is found to be in good agreement with the experimental value.